Aaah. I see. It seems much more obvious to me with the reduced regexes. I've never used such extensive regexes and I think I may have been letting myself get overwhelmed and distracted by the length and complexity of these statements in comparison to the shorter more basic code I've been learning with.
So in essence,

is not. In this stripped down form I can see how the last example, although interpreted properly by Perl, can look like a random if (x = y) and an unrelated block of { print x; }. I'm not entirely sure of what kind of examples you are asking for, but from this node:
...

if ($Age < 13) && ($Age > 0))
{
print "What are you doing here, $firstName? This Web
site is strictly PG-13. Shame on you for being so
naughty as to come here!";
}
elsif ($Age < 18) && ($Age > 12))
{
print "Not to long ago, we’d have have chased you away
from our Web site. But now that you’re a teenager and
mature enough for PG-13 materials, we’re glad to see
you $firstName.";
}

Thank you again for taking time out to help me grasp the fundamentals. Please let me know if I am missing your point. I enjoy Perl (and learning programming in general) and feel I have been progressing rather quickly, but I want to squash bad habits and form a good foundation in style and understanding before moving to some of the more complex concepts and modules in Perl.

Be aware that this book provides guidelines; not rules. Also, as it was released in 2005, it won't make references to features added in more recent versions of Perl (perlhist provides a history of Perl releases, if you're interested).